Position stick with automatic trim control

Abstract

Automatic trim control for a position stick. Strain gauges are mounted with respect to the position stick so as to generate signals proportional to the force manually exerted upon the control stick. The signals from the strain gauges are used to control trim motors which adjust force exerted by springs on the position stick in opposition to the manual force. The signals from the strain gauges are used to control the trim motors so as to reduce the force of the trim springs opposing the manual force. The trim springs are adjusted to reduce the opposition force to a minimum.

We claim: 
     
       1. An automatic trim control system for a manually repositionable position stick comprising: trim means for establishing a no-force position for said position stick;   a trim motor connected to said trim means for adjusting the no-force position along one directional component;   a strain gage bridge mounted relative to said position stick such that said strain gage bridge generates signals proportional to force exerted on said position stick caused by manual repositioning of said position stick along the one directional component; and   means for processing the signals generated by said strain gages to determine control signals to be directed to said trim motor to move the no-force position of said position stick along the one directional component in accordance with the manual repositioning of said position stick.   
     
     
       2. The automatic trim control system of claim 1 wherein said trim means comprises a trim spring. 
     
     
       3. The automatic trim control system of claim 1 further comprising a limit switch connected to said trim means and said trim motor and a diode electrically connected in parallel with said limit switch, said diode allowing signals to said trim motor to operate said trim motor in a direction so as to adjust said trim means away from the limit set by said limit switch. 
     
     
       4. The automatic trim control system of claim 1 wherein said processing means comprises: means for conditioning the signals from said strain gauge bridge so as to produce an output signal substantially linearly proportional to the force exerted on said position stick along the one directional component;   means for setting an upper threshold and a lower threshold and for issuing a command signal if the output signal exceeds the upper threshold or falls below the lower threshold; and   means responsive to the command signal for providing power to said trim motor.   
     
     
       5. The automatic trim control system of claim 4 wherein said means responsive to the command signal for providing power to said trim motor comprises an FET H bridge. 
     
     
       6. An-automatic trim control system for a position stick comprising: trim means for establishing a no-force position for said position stick;   a first trim motor connected to said trim means for adjusting the no-force position along a first directional component;   a second trim motor connected to said trim means for adjusting the no-force position along a second directional component different from the first direction;   a first strain gauge bridge connected to said position stick to generate signals corresponding to force exerted on said position stick along the first directional component;   means for conditioning the signals from said first strain gauge bridge so as to produce a first output signal substantially linearly proportional to the force along the first directional component;   means for setting an upper threshold and a lower threshold and for issuing a command signal if the first output signal exceeds the upper threshold or falls below the lower threshold;   means responsive to the command signal for providing power to said first trim motor;   a second strain gauge bridge connected to said position stick to generate signals corresponding to force exerted on said position stick along the second directional component;   means for conditioning the signals from said second strain gauge bridge so as to produce a second output signal substantially linearly proportional to the force along the second directional component;   means for setting an upper threshold and a lower threshold and for issuing a command signal if the second output signal exceeds the upper threshold or falls below the lower threshold; and   means responsive to the command signal for providing power to said second trim motor.   
     
     
       7. The automatic trim control system of claim 6 further comprising a limit switch connected to said trim means and said first trim motor and a diode electrically connected in parallel with said limit switch, said diode allowing signals to said first trim motor to operate said first trim motor in a direction so as to adjust said trim means away from the limit set by said limit switch. 
     
     
       8. The automatic trim control system of claim 6 wherein said trim means comprises lateral trim springs and longitudinal trim springs. 
     
     
       9. The automatic trim control system of claim 6 wherein said means responsive to the command signal for providing power to said first trim motor comprises an FET H bridge. 
     
     
       10. A cyclic control stick with automatic trim control comprising: a first mechanical control linkage;   a second mechanical control linkage;   a cyclic stock, having one end with a hand grip and an opposite end, being adjustably positionable so as to mechanically reposition said first mechanical linkage and said second mechanical linkage;   a first mechanical coupling between a first directional input from said cyclic stick and said first mechanical control linkage;   a second mechanical coupling between a second directional input from said cyclic stick and said second mechanical control linkage;   strain gages mounted proximate to the opposite end of said cyclic stick such that said strain gages generate signals proportional to force exerted on said cyclic stick caused by manual repositioning of said cyclic stick along a first directional input and signals proportional to force exerted on said cyclic stick caused by manual repositioning of said cyclic stick along a second directional input;   first trim means for applying force to said first mechanical coupling so as to oppose manual repositioning of said cyclic stick along the first directional input;   second trim means for applying force to said second mechanical coupling so as to oppose manual repositioning of said cyclic stick along the second directional input;   a first trim motor for adjusting the amount of force exerted on said first mechanical coupling by said first trim means;   a second trim motor for adjusting the amount of force exerted on said second mechanical coupling by said second trim means;   means for processing the signals generated by said strain gages to determine control signals to be directed to said first trim motor and said second trim motor to reduce the amount of the opposition force exerted on said first mechanical coupling and said second mechanical coupling to a minimum.   
     
     
       11. The cyclic control stick of claim 10 further comprising a pivot member, fixedly attached to said cyclic stick, having two flat surfaces perpendicular to one another and wherein said strain gages are mounted on said flat surfaces. 
     
     
       12. The cyclic control stick of claim 10 wherein said first trim means comprises a trim spring. 
     
     
       13. The cyclic control stick of claim 10 further comprising an FET H bridge electrically connected between said processing means and said first trim motor. 
     
     
       14. The cyclic control stick of claim 10 further comprising a limit switch connected to said first trim means and said first trim motor and a diode electrically connected in parallel with said limit switch, said diode allowing signals to said first trim motor to operate said first trim motor in a direction so as to adjust said trim means away from the limit set by said limit switch. 
     
     
       15. The cyclic control stick of claim 10 wherein said processing means comprises means for generating a command signal if the signals from said strain gauges exceeds an upper threshold or falls below a lower threshold.